Manually operable molded case circuit breaker with special trip testing means

ABSTRACT

A molded case circuit breaker with manually operable ON-OFF handle means, and a separate rotatable trip testing button in an opening in the cover of the breaker casing and flush with the surface thereof. The trip testing button includes two parts which when assembled trap the button rotatably in the casing cover. The interior portion of the trip testing button has two angularly extending arms and is of resilient plastic material. One of the arms engages the circuit breaker trip bar when the button is rotated, and causes tripping. The other arm of the trip testing button is thin and elongated and serves to position the button in normal unoperated position and to act as a spring to return the button from trip operating position to its normal position. Positive stops are also provided for limiting rotation in each direction.



1. An automatic electric circuit breaker compriSing: a. a casing of molded insulating material having a generally planar cover portion with a manually operable handle projecting through an opening therein for operating said circuit breaker between ON and OFF conditions; b. a trip bar in said casing movable from a normal position to a releasing position to cause automatic opening of said circuit breaker; c. a trip-testing button rotatably supported in said insulating casing, said testing button including an outer portion having a head accessible for operation externally of said insulating casing and an inner portion within said insulating casing; d. said inner portion of said trip testing button including a first elongated arm portion extending radially from the rotational axis of said button and terminating adjacent said trip bar; e. said test button being rotatable from a normal position to a tripping position to cause said elongated radial extension of said inner portion to engage said trip bar and cause tripping of said circuit breaker, and f. resilient means in said casing resiliently resisting rotation of said button from said normal position to said tripping position and returning said button to said normal position after rotation to said tripping position.
 2. An automatic electric circuit breaker as set forth in claim 1 wherein said resilient means comprises a second elongated portion extending radially from the rotation axis of said test button and engaging an abutment in said circuit breaker casing to resiliently retain said trip testing button in said normal position.
 3. An automatic electric circuit breaker as set forth in claim 2 wherein said inner portion of said trip-testing button comprises a unitary molded part of resilient plastic material, said first elongated portion of said inner portion being formed and dimensioned so as to be relatively rigid and not subject to significant deformation when said trip button is operated, and said second elongated extension being formed and dimensioned so as to be resiliently deformed upon rotation of said trip button.
 4. An automatic electric circuit breaker as set forth in claim 2 wherein said outer portion comprises a member molded of thermoplastic insulating material and includes a generally cylindrical portion closely fitting in said opening in said cover portion of said casing, a non-circular section stem portion extending through a conforming shape hole in said inner portion, and an outermost portion extending beyond said inner portion and thermally deformed to positively connect said inner and outer portions.
 5. An automatic electric circuit breaker as set forth in claim 2, including means carried by said insulating casing for positively limiting rotation of said test button in both clockwise and counter-clockwise directions. 